rtcd/win32: use InitializeCriticalSection explicitly

Protect the call to {Initialize,Delete}CriticalSection() with an
Interlocked{Inc,Dec}rement() pair, rather than the previous static
initialization. This should play better with AppVerifier, and fix issue

  http://code.google.com/p/webm/issues/detail?id=467

Change-Id: I06eadbfac1b3b4414adb8eac862ef9bd14bbe4ad